Dealer Finance Receivables Non-accretable Yield (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Receivables [Abstract]
Contractual Net Cash Flows	$ 56,287
Expected Net Cash Flows	(49,843)
Non-accretable Yield	$ 6,444

The amount of the loan's contractually required payments receivable in excess of the amount of its cash flows expected to be collected. This relates to loans originated through our indirect lending activities, for which it is probable, at origination, that the company will be unable to collect all contractually required payments receivable.

No definition available.

Name:	dta_NonAccretableYield
Namespace Prefix:	dta_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant